Despite detailed understanding of the cellular mechanisms leading to neuronal death following acute injury, acute brain injury is an important cause of neurologic disability in patients for which there is no treatment. I have found that F-68, a tri-block co-polymer of polyethylene and polypropylene, profoundly rescues neurons from severe injury in vitro and in vivo, by repairing the loss of neuronal plasma membrane integrity. Targeting the plasma membrane with this polymer constitutes a novel, effective, and potentially important treatment for rescuing neurons following acute injury. The major objective of this application is to understand how tri-block co-polymers interact with damaged membranes to rescue injured neurons. To achieve this objective, we will study the interactions of these co-polymers with increasingly complex membrane systems: giant unilamellar vesicles (GUVs), sealed erythrocyte ghosts and cultured hippocampal neurons. The Specific Aims of this proposal are: 1) Identify the role played by co-polymer architecture in the efficacy of membrane repair and the importance of co-polymer architecture in neuroprotection. 2) Identify the role played by lipid packing density in inducing F-68 insertion into and repair of the plasma membrane. 3) Identify the role played by co- polymers in decreasing oxidative stress and peroxidative plasma membrane damage during acute injury. 4) Identify the role played by membrane lipid peroxidation and changes in membrane fluidity in inducing F-68 insertion into and repair of the plasma membrane.